Method for transmitting mbsfn subframe configuration information of neighboring cells

ABSTRACT

A method and an apparatus for transmitting multimedia broadcast single-frequency network (MBSFN) subframe configuration information of neighboring cells in a wireless system is provided. The method comprises: transmitting, by a base station of a serving cell, MBSFN subframe configuration information of the serving cell to a UE which accepts services from the serving cell via a broadcast control channel (BCCH); transmitting information on a subset relationship of MBSFN subframe configurations of the neighboring cells relative to the MBSFN subframe configuration of the serving cell to the UE which accepts services from the serving cell via the broadcast control channel (BCCH); performing, by the UE, measurements on the neighboring cells according to the subframe configuration information of the serving cell and the information on the subset relationship of the MBSFN subframe configurations of the neighboring cells relative to the MBSFN subframe configuration of the serving cell.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of a prior applicationSer. No. 13/148,801, filed on Nov. 9, 2011, which is a U.S. NationalStage application under 35 U.S.C. §371 of an International applicationfiled on Feb. 9, 2010 and assigned application number PCT/KR2010/000776,which claimed the benefit of a Chinese patent application filed on Feb.10, 2009 in the Chinese Patent Office and assigned Serial number200910005875.X and of a Chinese patent application filed on Feb. 11,2009 in the Chinese Patent Office and assigned Serial number200910004211.1, the entire disclosure of each of which is herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to wireless communication system, inparticular to a method for indicating MBSFN subframe configurationinformation of neighboring cells and completing signal powermeasurements on the neighboring cells in a wireless communicationsystem.

BACKGROUND ART

At present, many advanced and matured techniques, like OFDM modulationand MIMO antenna, are applied in wireless technology development. Withthe incoming completion of standardization of these new wirelesstechniques, the performance of a wireless network in terms of throughputand delay has been greatly improved. In a new wireless system, the LTE(Long Term Evolution) network technique is a representative wirelesstechnique based on OFDM and MIMO. It is currently supported by manyoperators and providers.

An LTE system supports Multi-cast data transmission in addition to theconventional Uni-cast data transmission. Specifically, FIG. 1 shows thecomposition of an LTE physical-layer frame. In an LTE system, a 10ms-long transmission frame 101 is divided into 10 subframes 102 at aninterval of 1 ms. Here, some of the subframes can be defined by thesystem as subframes for Multi-cast transmission. In the subframessupporting Multi-cast transmission, Uni-cast data can be mixed andtransmitted in a specified format with TDM multiplexing.

In an OFDM system, when all cells share a single frequency fortransmission, in the edge of each cell, signal enhancement can be gainedwith subframes in Multi-cast transmission for the same transmissioncontent. Therefore, a system in which multimedia broadcast informationis transmitted in Multi-cast service and the cells share a singlefrequency for transmission is called MBSFN (Multimedia BroadcastSingle-frequency network).

In the MBSFN, a user equipment (UE) can obtain MBSFN configurationinformation of a cell where the UE is located, i.e., specific subframeinformation on configuration of data transmission in MBSFN mode(subframe number), by reading a broadcast control channel (BCCH). Withthe system information transmitted via the BCCH, UE can also obtain theMBSFN information on neighboring cells relative to the serving cell. Atpresent, the LTE standard specification has already supported suchbroadcast of the neighboring cell MBSFN configuration information. Inthe broadcast information, however, some problem exists in messagedefinition, which tends to make the UE unable to accurately learn aboutMBSFN configurations of the neighboring cells, and thus unable toaccurately obtain a strategy for measuring the signals from theneighboring cells. The present invention is made in view of the aboveproblem.

The LTE system is divided into two types of Frame type 1 (MD) and Frametype 2 (TDD) according to the schemes of TDD and FDD. For these twoframes structures, SCH (synchronization channel) is transmitted via thezeroth and the fifth subframes in Frame Type 1, and the SCH istransmitted via the first and the sixth subframes in Frame Type 2. Ifthe MBSFN information of one of the neighboring cells can not becorrectly transmitted to the UE in the serving cell, the UE is likely toassume all of the subframes, except the one for SCH transmission, areMBSFN subframes in the neighboring cell. Therefore, the UE can performsignal strength measurement only on the subframes for SCH transmission,which results in a degradation of the performance of signal strengthmeasurement for the neighboring cell The present invention can avoid theabove disadvantage by perfecting message definition in the currentstandard.

SUMMARY

An object of the present invention is to provide a method for indicatingMBSFN subframe configuration information of neighboring cells and thusoptimizing measurement on the neighboring cells.

To achieve the object mentioned above, a method for transmitting, by abase station, MBSFN subframe configuration information of neighboringcells comprises steps of:

transmitting, by a base station of a serving cell, MBSFN subframeconfiguration information of the serving cell to a UE which acceptsservices from the serving cell via a broadcast control channel (BCCH);

transmitting, by the base station of the serving cell, information on asubset relationship of MBSFN subframe configurations of the neighboringcells relative to the MBSFN subframe configuration of the serving cellto the UE which accepts services from the serving cell via the broadcastcontrol channel (BCCH);

performing, by the UE, measurements on the neighboring cells accordingto the subframe configuration information of the serving cell and theinformation on the subset relationship of the MBSFN subframeconfigurations of the neighboring cells relative to the MBSFN subframeconfiguration of the serving cell.

With the method of the present invention, the UE can learn about theMBSFN subframe configuration information of the neighboring cells in amore accurately manner. Therefore, more subframes can be measured toimprove measurement accuracy. Meanwhile, the present invention is basedon redefinition of messages in the existing method, and thus no extrasignaling overhead will be introduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the basic frame structure of the LTE system;

FIG. 2 shows a method for transmitting, by BS, MBSFN subframeconfiguration information of neighboring cells to a UE according to afirst embodiment;

FIG. 3 shows a process that the BS of the serving cell transmits theMBSFN subframe configuration information of the neighboring cells to theUE in the first embodiment.

DETAILED DESCRIPTION

In the following, detailed descriptions of well-known functions orequipments are omitted, to avoid any redundancy.

Now, the present invention is described with reference to FIG. 2.

At Step 201, a BS of the serving cell transmits the MBSFN subframeconfiguration information of the serving cell to a UE in the servingcell via a broadcast control channel (BCCH).

At Step 202, the BS of the serving cell transmits to the UE informationon a subset relationship of the MBSFN subframe configurations ofneighboring cells relative to the MBSFN subframe configuration of theserving cell to the UE in the serving cell.

The above information on the subset relationship of the MBSFN subframeconfigurations of the neighboring cells relative to the MBSFN subframeconfiguration of the serving cell can be transmitted to the UE withRadio Resource Control signaling (RRC signaling) or via the broadcastcontrol channel (BCCH).

According to one implementation of the present embodiment, theinformation on the subset relationship of the MBSFN subframeconfigurations of the neighboring cells relative to the MBSFN subframeconfiguration of the serving cell is illustrated in Table 1 as follows.

Table 1: Information on the subset relationship of the MBSFN subframeconfigurations of the neighboring cells relative to the MBSFN subframeconfiguration of the serving cell transmitted from the serving cell tothe UE

TABLE 1 Description of subframe configuration information of neighboringcells Subframe configurations of neighboring cells: to provide MBSFNsubframe configuration information of intra-frequency neighboring cells:00: MBSFN subframe configurations of some of the neighboring cells arenot a subset of the subframe configuration of the serving cell; 10:MBSFN subframe configurations of all the neighboring cells are subsetsof the subframe configuration of the serving cell; 01: No MBSFNsubframes are present in all neighbour cells.

According to a further implementation of the present embodiment, theinformation on the subset relationship of the MBSFN subframeconfigurations of the neighboring cells relative to the MBSFN subframeconfiguration of the serving cell is illustrated in Table 2 as follows.

Table 2: Information on the subset relationship of the MBSFN subframeconfigurations of the neighboring cells relative to the MBSFN subframeconfiguration of the serving cell transmitted from the serving cell tothe UE

TABLE 2 Description of subframe configuration information of neighboringcells Subframe configurations of neighboring cells: to provide MBSFNsubframe configuration information of intra-frequency neighboring cells:00: MBSFN subframe configurations of some of the neighboring cells arenot a subset of the subframe configuration of the serving cell; 10:MBSFN subframe configurations of all the neighboring cells are subsetsof the subframe configuration of the serving cell; 01: No MBSFN subframes are present in all neighbour cells.

According to still a further implementation of the present embodiment,the information on the subset relationship of the MBSFN subframeconfigurations of the neighboring cells relative to the MBSFN subframeconfiguration of the serving cell is illustrated in Table 3 as follows.

Table 3: Information on the subset relationship of the MBSFN subframeconfigurations of the neighboring cells relative to the MBSFN subframeconfiguration of the serving cell transmitted from the serving cell tothe UE

TABLE 3 Description of subframe configuration information of neighboringcells Subframe configurations of neighboring cells: to provide MBSFNsubframe configuration information of intra-frequency neighboring cellsand inter-frequency neighboring cells: 00: MBSFN subframe configurationsof some of the neighboring cells are not a subset of the subframeconfiguration of the serving cell; 10: MBSFN subframe configurations ofall the neighboring cells are subsets of the subframe configuration ofthe serving cell; 01: No MBSFN subframes are present in all neighbourcells.

With the above description of subframe configuration information ofneighboring cells, if “no MBSFN subframes are present in all neighbourcells”, the BS of the serving cell transmits “01” to the UE; if “MBSFNsubframe configurations of all the neighboring cells are subsets of thesubframe configuration of the serving cell”, the BS of the serving celltransmits “10” to the UE; and if “MBSFN subframe configurations of someof the neighboring cells are not a subset of the subframe configurationof the serving cell”, the BS of the serving cell transmits “00” to theUE.

At Step 203, according to the subframe configuration information of theserving cell and the information on the subset relationship of the MBSFNsubframe configurations of the neighboring cells relative to thesubframe configuration of the serving cell, the UE implements respectivemeasurements on the neighboring cells.

For an LTE Frame Type 1 system, if information on the subsetrelationship of the MBSFN subframe configurations of the neighboringcells relative to the MBSFN subframe configuration of the serving cellreceived by the UE from the BS of the serving cell is “00”, the UEperforms measurement on only the subframe #0 or the subframe #5 of therespective neighboring cell; if the subset relationship information isindicated as “10”, the UE performs measurement on the subframes of theneighboring cell that are the same as the measurement subframes of theserving cell; and if the subset relationship information is indicated as“01”, the UE can performs measurement on all subframes of theneighboring cell.

In the present embodiment, the process that the BS of the serving celltransmits the MBSFN subframe configuration information of theneighboring cells to the UE is illustrated in FIG. 3.

As shown in FIG. 3, the MBSFN subframe configuration information of theneighboring cells is transmitted to the UE via the broadcast controlchannel (BCCH). If none of the neighboring cells is configured with aMBSFN subframe, “01” is transmitted to the UE; if MBSFN subframeconfigurations of all the neighboring cells are a subset of the subframeconfiguration of the serving cell, “10” is transmitted to the UE;otherwise, “00” is transmitted to the UE.

What is claimed is:
 1. A method for receiving multimedia broadcastsingle-frequency network (MBSFN) subframe configuration information of aneighboring cell by a terminal, the method comprising: receiving firstinformation on a MBSFN subframe configuration of a serving cell from abase station of the serving cell; receiving second information on aneighboring cell configuration from the base station, the secondinformation includes information related to a MBSFN subframeconfiguration of at least one neighboring cell relative to the firstinformation of the serving cell; and measuring a signal of the at leastone neighboring cell on a subframe based on the first information andthe second information.
 2. The method of claim 1, wherein the at leastone neighboring cell is an intra-frequency neighboring cell.
 3. Themethod of claim 1, wherein the at least one neighboring cell is aninter-frequency neighboring cell.
 4. The method of claim 1, wherein thesecond information includes a first value, if no MBSFN subframes arepresent in the at least one neighboring cell, a second value, if MBSFNsubframe configurations of a plurality of neighboring cells are subsetsof the MBSFN subframe configuration of the serving cell, and a thirdvalue, if the MBSFN subframe configurations of some of the plurality ofneighboring cells are not a subset of the MBSFN subframe configurationof the serving cell.
 5. The method of claim 4, wherein a same value isincluded in the second information in the case where the MBSFN subframeconfigurations of all of the plurality of neighboring cells areidentical and the MBSFN subframe configurations of all of the pluralityof neighboring cells being included in the subframe configuration of theserving cell.
 6. The method of claim 4, wherein the subframe formeasuring the signal of the at least one neighboring cell is determinedbased on the second information, wherein, if the second informationincludes the first value, the subframes associated with the measurementinformation are preset subframes, wherein, if the second informationincludes the second value, the subframes associated with the measurementinformation are subframes of the neighboring cells that are the same asthe measurement subframes of the serving cell, and wherein, if thesecond information includes the third value, the subframes associatedwith the measurement information are all subframes of the plurality ofneighboring cells.
 7. The method of claim 1, wherein the secondinformation is received via radio resource control (RRC) signaling.
 8. Aterminal for receiving multimedia broadcast single-frequency network(MBSFN) subframe configuration information of a neighboring cell, theterminal comprising: a transceiver configured to transmit and receive asignal; and a controller configured to: receive first information on aMBSFN subframe configuration of a serving cell from a base station ofthe serving cell, receive second information on a neighboring cellconfiguration from the base station, the second information includesinformation related to a MBSFN subframe configuration of at least oneneighboring cell relative to the first information of the serving cell,and measure a signal of the at least one neighboring cell on a subframebased on the first information and the second information.
 9. Theterminal of claim 8, wherein the at least one neighboring cell is anintra-frequency neighboring cell.
 10. The terminal of claim 8, whereinthe at least one neighboring cell is an inter-frequency neighboringcell.
 11. The terminal of claim 8, wherein the second informationincludes a first value, if no MBSFN subframes are present in the atleast one neighboring cell, a second value, if MBSFN subframeconfigurations of a plurality of neighboring cells are subsets of theMBSFN subframe configuration of the serving cell, and a third value, ifthe MBSFN subframe configurations of some of the plurality ofneighboring cells are not a subset of the MBSFN subframe configurationof the serving cell.
 12. The terminal of claim 11, wherein a same valueis included in the second information in the case where the MBSFNsubframe configurations of all of the plurality of neighboring cells areidentical and the MBSFN subframe configurations of all of the pluralityof neighboring cells being included in the subframe configuration of theserving cell.
 13. The terminal of claim 11, wherein the subframe formeasuring the signal of the at least one neighboring cell is determinedbased on the second information, wherein, if the second informationincludes the first value, the subframes associated with the measurementinformation are preset subframes, wherein, if the second informationincludes the second value, the subframes associated with the measurementinformation are subframes of the neighboring cells that are the same asthe measurement subframes of the serving cell, and wherein, if thesecond information includes the third value, the subframes associatedwith the measurement information are all subframes of the plurality ofneighboring cells.
 14. The terminal of claim 8, wherein the secondinformation is received via radio resource control (RRC) signaling. 15.A method for transmitting multimedia broadcast single-frequency network(MBSFN) subframe configuration information of a neighboring cell by abase station, the method comprising: transmitting first information onMBSFN subframe configuration of a serving cell to a terminal in aserving cell of the base station; transmitting second information onneighboring cell configuration to the terminal, the second informationincludes information related to MBSFN subframe configuration of at leastone neighboring cell relative to the first information of the servingcell; and receiving measurement information of the at least oneneighboring cells from the terminal, wherein a signal of the at leastone neighboring cell on a subframe for the measurement information ismeasured based on the first information and the second information. 16.The method of claim 15, wherein the at least one neighboring cell isintra-frequency neighboring cell.
 17. The method of claim 15, whereinthe at least one neighboring cell is inter-frequency neighboring cell.18. The method of claim 15, wherein the second information includes afirst value, if no MBSFN subframes are present in the at least oneneighboring cell, a second value, if MBSFN subframe configurations of aplurality of neighboring cells are subsets of the MBSFN subframeconfiguration of the serving cell, and a third value, if the MBSFNsubframe configurations of some of the plurality of neighboring cellsare not a subset of the MBSFN subframe configuration of the servingcell.
 19. The method of claim 18, wherein a same value is included inthe second information in the case where the MBSFN subframeconfigurations of all of the plurality of neighboring cells areidentical and the MBSFN subframe configurations of all of the pluralityof neighboring cells being included in the subframe configuration of theserving cell.
 20. The method of claim 18, wherein the subframe formeasuring the signal of the at least one neighboring cell is determinedbased on the second information, wherein, if the second informationincludes the first value, the subframes associated with the measurementinformation are preset subframes, wherein, if the second informationincludes the second value, the subframes associated with the measurementinformation are subframes of the neighboring cells that are the same asthe measurement subframes of the serving cell, and wherein, if thesecond information includes the third value, the subframes associatedwith the measurement information are all subframes of the plurality ofneighboring cells.
 21. The method of claim 15, wherein the secondinformation is received via radio resource control (RRC) signaling. 22.A base station for transmitting multimedia broadcast single-frequencynetwork (MBSFN) subframe configuration information of a neighboringcell, the base station comprising: a transceiver configured to transmitand receive a signal; and a controller configured to: transmit firstinformation on MBSFN subframe configuration of a serving cell to aterminal in a serving cell of the base station, transmit secondinformation on neighboring cell configuration to the terminal, thesecond information includes information related to MBSFN subframeconfiguration of at least one neighboring cell relative to the firstinformation of the serving cell, and receive measurement information ofthe at least one neighboring cells from the terminal; wherein a signalof the at least one neighboring cell on a subframe for the measurementinformation is measured based on the first information and the secondinformation.
 23. The base station of claim 22, wherein the at least oneneighboring cell is intra-frequency neighboring cell.
 24. The basestation of claim 22, wherein the at least one neighboring cell isinter-frequency neighboring cell.
 25. The base station of claim 22,wherein the second information includes a first value, if no MBSFNsubframes are present in the at least one neighboring cell, a secondvalue, if MBSFN subframe configurations of a plurality of neighboringcells are subsets of the MBSFN subframe configuration of the servingcell, and a third value, if the MBSFN subframe configurations of some ofthe plurality of neighboring cells are not a subset of the MBSFNsubframe configuration of the serving cell.
 26. The base station ofclaim 25, wherein a same value is included in the second information inthe case where the MBSFN subframe configurations of all of the pluralityof neighboring cells are identical and the MBSFN subframe configurationsof all of the plurality of neighboring cells being included in thesubframe configuration of the serving cell.
 27. The base station ofclaim 25, wherein the subframe for measuring the signal of the at leastone neighboring cell is determined based on the second information,wherein, if the second information includes the first value, thesubframes associated with the measurement information are presetsubframes, wherein, if the second information includes the second value,the subframes associated with the measurement information are subframesof the neighboring cells that are the same as the measurement subframesof the serving cell, and wherein, if the second information includes thethird value, the subframes associated with the measurement informationare all subframes of the plurality of neighboring cells.
 28. The basestation of claim 22, wherein the second information is received viaradio resource control (RRC) signaling.